Hydraulic power transmission for presses



Dec. 19, 1944. R. V ON ROTZ HYDRAULIC POWER TRANSMISSIQN FOR PRESSES Filed May 1.4, 1943 J i a 4 m a .6 E 4 9 Q m M 3 I w 42 :3 W a v J :17 gag! 2 a x. K f u a 7 F/ M a, 2 W WW5 3 g 1 a 2 m 3 4 9 J 4 w mfii m l J n 0 a 1 0 3 z 4 L Al a 2 TH Ha 1 4 w w PEJHII n1 w n IE. I 7 v g 5 1 w 4 II a M a E o Patented l9, 1944 UNiTED STATES PAiE HYDRAULIC POWER TRANSMISSION FOR PRESSES Robert Von am, Manhasset N. '31. Application my 14, 1943, Serial no. 487,804

- 2 Claims.

My-invention relatesto hydraulic transmissions for presses of the rapid reciprocating head type used for continuous punching and shearing operations in connection with the stamping and forming of articles from sheet metal, leather, plastics, and like materials. Y

In mechanical presses of this class, the reciprocating head is generally driven by a crank and connecting rod in combination with a continu- -ously rotating fly-wheel and clutch. With this arrangement, the actual pressure developed on the material is uncertain. The mechanical parts of th press are subject to high indeterminate loads and stresses which result in rapid wear, and

frequent mechanical failures.

In conventional-hydraulic presses of this class,

relatively. large capacity pump in combination with a reversing valve is commonly used to reciprocate the head by means of a cylinder and piston. In this'arrangement the maximum oming pressure is required only over a very 1 portion of the stroke cycle, consequently the hydraulic power transmission equipment is usually large and cumbersome, and due to.the nature of the operating cycle. unctions at relatively low efllciency.

It is the purpose of this invention to provide a combinaiton of hydraulic and mechanical elements which embody a unique power transmission system as applied to acpress which will be capable of delivering pressure strokes. at high distributor valve 2|, included in Figure 1. Figure 3 is a detailed showing in section of the,

distributorvalve 21, included in Figure 1.'

Having reference to Figure l, a platen or head i is attached to piston rod 2 slidable in cylinder i9 and free to move in response to fluid pressure on piston 28. r The piston rod 2 is recessed to receive part 11 having a central opening to admit fluid to chamber 28. I s. 7 7

Cylinders land I with their respective plunger-s (Cl. B0.52)

8 and I comprise a high pressure pumping unit. The adjacent ends 01' these plungersare provided with rollers which abut cam l8. This cam s is rigidly attached to rotatableshaft 22 carried in suitable bearings not shown. A flywheel M is keyed to she 22, and is caused to rotate by an external sour Springs 28 and 24 maintain the I plungers in contact with the cam i8 at all times.

It is obvious that as flywheel M, shaft 22.- and lo cam I 8 are caused to rotate by any suitable prime mover, plungers 8 and I are caused ,to reciprocate alternately. Fluid thus drawn from reservdir 8 thru check valves 8 and 28 is directed to oppositeends of cylinder is thru conduits i8 and 28.

'15 Numeral il represents a low-pressure;rotary pump of any suitable construction, and i2 an adjustable pressure relief valve of any suitable type. Numeral 3 represents a storage reservoir for the hydraulic fluid, usually oil. In direct communi- 20 cation with the reservoir 3 is a pressure responsive shut of! valve 8 of conventional type., This valve operates to contrcl the flow of fluid between the lower part oi cylinder l8 and the reservoir} through conduit l3. Fluid under pressure for the opening and closing of valve 8 isprovided by the low pressure pump ll.

A mechanically operated distributing valve 21 is arranged to control the application 'oifluid under pressure from pump II to valve 8 so'that 30 actuation of valve 21 controls the flow of fluid Y between-conduit I8 anthi eservoir 3 through valve 8. Valye 21 is arranged to be actuated by a cam,

not shown, attached to shaft 22 in such a manner that rotation of shaft 22 and the cam causes 5 pressuretb be directed to valve 8 so as to maintain it in the open position at all times except during the upward or pressure stroke of plunger 8. During the pressure stroke or plunger 8, valve 21 is actuated by the position of said cam so as to 40 close valve 8.

Valve i8 is an adjustable pressure reliefvalve l of conventional type which is in communication with line 28 through conduit 38 and is connected to 'line l8 through conduit". Valve 82 isan adjustable pressure-relief valveoi'flsimilar construction which is connected to line 28 through conduit 38 and to line I8 through conduit 81.

Pressure from pump Ii through supply. line 88' is directed to the pressure operated shut oi! valve 8 by distributing valve 21 through conduits 88 and a. Exhaust fluid from valve 0 is directed toreturnline I! through distributor valve 21 and conduit 8i.

' to distributing valve 2! through conduit '48. 1 as Valve 2| is in communication with chamber 28 NT ,oFricaI Pressure from pump, Ii is directem through passage 20 and conduits and 48.

Valve 2| is also connected to line 28 through conduit 42. Valve 8 is a check valve of conventional type which permits flow in one direction only,

namely, from line ll through conduit 48 to line 28. Check valve 2! of similar construction permits flow from line ll to conduit 3| through line area at the rod end and a large effective area at the head end. With the arrangement shown a relatively long opening stroke of the piston is obtained with a small displacement of fluid.

The operation of my mechanism is as follows: Fluid under low pressure from pump H is directed thru conduit 20 to chamber 2 so as to exert pressure on piston rod 2 tending to, urge it upward. Pressure is therefore developed on the fluid in the rod end of cylinder l9, conduit 28, and the chamber of cylinder 5. As cam it rotates counter clockwise from the position shown, plunger I is displaced so that high pressure fluid is directed to the rod end of cylinder l9. Piston rod 2 is thus caused to movedownward. Fluid from the opposite end of the cylinder is displaced thru conduit i3 and valve 8 which is open. Fluid from chamber 28 together with the low pressure pump delivery is displaced thru relief valve I! to reservoir 3. ,As the cam ll continues to rotate, plunger I is displaced by spring 24 so that oil from the rod end of cylinderi9 is withdrawn permlttinggthe head I to rise and contact the work It in response to the pressure maintained in chamber 28.

. As shaft 22 rotates further, valve 21 is actuated so as to close valve 8. The further rotation of Smreo'm the flywheel, is utilized to develop a high' fluid pressure in-cylinder I which is transmitted by the means indicated to the work. As cam it continues to rotate, spring 23 displaces plunger so as to draw in fluid from reservoir I thrucheck valve 2!.

This cycle is repeated as long as flywheel M with shaft 2! and cam it are caused to rotate,

and valve 2| is shifted to direct pressure from pump Ii to chamber II. It is apparentthat there will be one complete operating cycle for each revolution of theflywheel. when valve 2| is manually shifted so asto di- 3 rect pressure thru conduit 26 to the rod end of cylinder it, the press is maintained in the open position as may be required for setting up, adjusting or loading.

This invention is not intended to be limited to the form shown in the drawing which is understood to be illustrative and diagrammatic only.

' I claim: y x

1. In a hydraulic power transmission mechanism, pump plungers mounted to slide in cylin- 5 dam, and arranged to be reciprocated in said cylinders by a rotating cam, and adapted upon their movement to displaces liquid, a shaft arranged to be rotated by an xternal power source; a flywheel and earns attached to said shaft and disposed to impart reciprocating motion to said plungers in opposite phase relationship by its rotation, a work cylinder with a piston and piston I rod mounted to slide in said cylinder and conduits connecting the pump cylinders with opposite ends of the work cylinder, an auxiliary pump -driven by an external power source to supply fluid at low pressure to rapidly advance the work slide, ,a hydraulic fluid reservoir with a conduit connecting said reservoir to said work cylinder, a 30 cut-ofl valve between said conduit and said reservoir arranged to be operated in timed relation to the working strokes of the piston.

I 2. In a hydraulic power transmission mechanism, a high pressure pump comprising plungers, slidable in cylinders and adapted to be driven in opposite phase relationshinby a cam attached to a rotary shaft, a differential work cylinder having a work piston provided with a supplementary expansible chamber for low pressure fluid, a low .pressure pump for supplying fluid to -said chamber to rapidly advance the work piston. a

cut-oil valve in the work cylinder conduit to confine the high pressure during the working str ke,-

a timing valve for directing fluid to the cu -oil' valve in timed relation to the power strokes of the piston, a manually operated distributing valve arranged to direct delivery of th low pressure pump to the work cylinder for starting and stopping the automatic operation of the piston at the will "of the operator. l ROBERT Von ROTZ' 

